Ceramic filter with window coupling

ABSTRACT

The present application is directed to a filter and methods of transmitting a signal through the filter. The filter includes a pair of adjoined blocks of dielectric material. A top surface of each block has a conductive patterned region. The filter also includes plural spaced apart through-holes extending through each block from the top surface to a bottom surface. The through-holes are partially surrounded by the patterned region. The filter also includes a peripheral window disposed between the adjoined blocks to permit a coupling between adjacent through-holes of the adjoined blocks. The filter also includes an in-line window and/or a crenellation located within a block of the pair of blocks and disposed between adjacent through-holes of the block to limit or tune coupling between the adjacent through-holes. The application is also directed to a system including a printed circuit board and a filter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication No. 62/418,979 filed Nov. 8, 2016, entitled “Ceramic Filterwith Window Coupling,” the content of which is incorporated by referencein its entirety herein.

FIELD

The present disclosure is generally related to ceramic filters, and moreparticularly, to a ceramic filter with a window coupling for adjoiningone or more other ceramic filters.

BACKGROUND

Ceramic filters are used in radio equipment to reduce interference. Inparticular, ceramic duplex filters including two individual band-passfilters are often employed. For example, one filter connects thereceiving branch and has a center frequency and bandwidth correspondingto the receiving band, while the other filter connects the transmissionbranch and has a center frequency and bandwidth corresponding to thetransmission band.

Existing recessed top pattern (RTP) filters are large, which limitstheir reliable manufacture. Furthermore, such filters arearchitecturally limited by the requirement that the strongest bulk fieldcouplings only occur to the next in-line resonator (withoutskip-resonator field couplings that would improve filter roll off).Also, such filters have undesired inter-resonator couplings due to thein-line architecture and the unconstrained fields around each resonator.

Conventional ceramic monoblock filters have resonator-to-resonatorcouplings limited to a straight-line path. This is due to each resonatorhaving a strong coupling tendency primarily to its nearest neighborswithin the ceramic block. This restriction to a straight-line pathlimits the design options for the filter. In turn, this limits theachievable filter response and the achievable small size of the filterbased on the required filter response. There also exists strongundesired coupling between resonators in the straight-line path that arenot adjacent. This is due to unimpeded electromagnetic fields thatextend into the entire monoblock structure.

Thus, there is a need to couple resonators that are not in astraight-line path. There is a further need to permit coupling betweenresonators in adjacent blocks in a duplex filter, and also to preventcoupling between some resonators in the straight-line path of eachblock.

SUMMARY

The foregoing needs are met, to a great extent, by the presentdisclosure, with an apparatus and method that permits coupling betweenresonators in adjacent monoblocks. The application also describesmethods and apparatuses that prevent coupling between some resonators inthe straight-line path. Filters designed employing these attributesexhibit the advantages of improved filter response. This is due to anincreased number of transmission zeroes in the transfer function,improved removal of unwanted couplings, and greater precision.

One aspect of the present disclosure is directed to a duplex filtercomprising a pair of adjoined blocks of dielectric material, each blockhaving a top surface including a conductive patterned region, a bottomsurface, and side surfaces. Plural spaced apart through-holes extendthrough each block from the top surface to the bottom surface, thethrough-holes being partially surrounded by the patterned region. A wallextends from the top surface of each block, the wall having an innersurface, an outer surface, and a roof. A peripheral window may bedisposed between the adjoined blocks to limit or tune coupling betweenadjacent through-holes of the adjoined blocks. The peripheral window maybe rectangular-shaped, square-shaped, cross-shaped, U-shaped,slit-shaped, oval-shaped, or circular shaped. Further, the peripheralwindow defines an opening.

In another aspect of the application, the duplex filter may alsocomprise an in-line window located within a block of the pair of blocksand disposed between adjacent through-holes of the block to limit ortune coupling between the adjacent through-holes. A width of the in-linewindow may be larger than a diameter of the adjacent through-holes. Aheight of the in-line window may be smaller than a longitudinal lengthof the adjacent through-holes. The in-line window may berectangular-shaped, square-shaped, cross-shaped, U-shaped, slit-shaped,oval-shaped, or circular shaped.

In another aspect of the application, the duplex filter may include acrenellation on the side surface of a block of the pair of blocks tolimit or tune coupling between adjacent through-holes within the blockand to reduce coupling between non-adjacent through-holes within theblock. A corresponding crenellation may be provided on the side surfaceof the other block of the pair of blocks, such that the pair ofcrenellations are aligned and form a hollow space therebetween. Thecrenellation defines a recess located on a major side surface of theblock. The recess may be rectangular-shaped, square-shaped,cross-shaped, U-shaped, slit-shaped, oval-shaped, or circular shaped.

In another aspect of the application, the duplex filter may includeplural peripheral windows and plural crenellations alternatinglyarranged along a length of the pair of blocks. The peripheral windowsand crenellations may be equidistantly spaced apart.

Another aspect of the application is directed to a system comprising aprinted circuit board having a top surface and including input andoutput connections; and a duplex filter. The duplex filter includes aplurality of adjoined blocks of dielectric material, each block having atop surface including a conductive patterned region, a bottom surface,and side surfaces. The duplex filter further includes plural spacedapart through-holes extending through each block from the top surface tothe bottom surface, the through-holes being partially surrounded by thepatterned region. The duplex filter also includes a wall extending fromthe top surface of each block, the wall having an inner surface, anouter surface, and a roof. A peripheral window may be disposed betweenthe adjoined blocks to permit coupling between adjacent through-holes ofthe adjoined blocks. Further, an in-line window may be located within ablock of the pair of blocks and disposed between adjacent through-holesof the block to limit or tune coupling between the adjacentthrough-holes. Further, a crenellation may be provided on the sidesurface of a block of the pair of blocks to limit or tune couplingbetween adjacent through-holes within the block and to reduce couplingbetween non-adjacent through-holes within the block. In an aspect of theapplication, the duplex filter further comprises plural peripheralwindows and plural crenellations alternatingly arranged along a lengthof a major side surface of the pair of blocks.

Another aspect of the application is directed to a method ofcommunicating a signal to and from a node. The method comprisesproviding a duplex filter; receiving the signal into the duplex filterfrom the node; transmitting the signal between adjacent through-holeswithin adjoined blocks of the duplex filter by passing the signalthrough a peripheral window located on a major side surface of theduplex filter; and sending the signal from the duplex filter out to thenode. The signal may be transmitted between adjacent through-holeswithin a block of the duplex filter by passing the signal through anin-line window located within the block. The signal may be transmittedbetween adjacent through-holes within a block of the duplex filter bypassing the signal by a crenellation located on a major side surface ofthe block.

There has thus been outlined, rather broadly, certain embodiments of theinvention in order that the detailed description thereof herein may bebetter understood, and in order that the present contribution to the artmay be better appreciated. There are, of course, additional embodimentsof the invention that will be described below and which will form thesubject matter of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to facilitate a fuller understanding of the invention,reference is now made to the accompanying drawings, in which likeelements are referenced with like numerals. These drawings should not beconstrued as limiting the invention and intended only to beillustrative.

FIG. 1 illustrates a partially transparent schematic view of a duplexfilter according to an aspect of the application.

FIG. 2 illustrates a partially transparent schematic view of a duplexfilter according to an aspect of the application.

FIG. 3 illustrates a duplex filter according to an aspect of theapplication.

FIG. 4 illustrates a system including a duplex filter on a printedcircuit board according to an aspect of the application.

DETAILED DESCRIPTION

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of embodiments inaddition to those described and of being practiced and carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein, as well as the abstract, are for thepurpose of description and should not be regarded as limiting.

Reference in this application to “one embodiment,” “an embodiment,” “oneor more embodiments,” or the like means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the disclosure. Theappearances of, for example, the phrases “an embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment, nor are separate or alternative embodiments mutuallyexclusive of other embodiments. Moreover, various features are describedwhich may be exhibited by some embodiments and not by the other.Similarly, various requirements are described which may be requirementsfor some embodiments but not by other embodiments.

It has been determined by the inventors and described herein that theinventive techniques provide improved ceramic filters with windows thatpermit resonators to be coupled to other resonators in which: 1)specific couplings can be designed for the best filter performance; 2)unwanted couplings can be largely removed; 3) the filter can be composedof smaller individual blocks that are easier to precisely manufacture;4) and the resultant filter can be smaller due to the design andinclusion of the window couplings.

FIG. 1 illustrates a schematic view of a ceramic duplex filter 10 inaccordance with an aspect of the present application. The duplex filter10 includes a first block 20 of dielectric material and a second block30 of dielectric material. Each block 20, 30 includes a respective topsurface 22, 32 having a conductive patterned region, a bottom surface24, 34, and side surfaces 26, 36. The respective side surfaces 26, 36further include major side surfaces 26 a, 36 a and minor side surfaces26 b, 36 b. The first and second blocks 20, 30 are adjoined at theirrespective major side surfaces 26 a, 36 a.

Each block 20, 30 also includes plural spaced apart through-holes 28, 38extending through each block from the top surface 22, 32 to the bottomsurface 24, 34. The through-holes are partially surrounded by thepatterned region and act as resonators. Further, a wall extends from thetop surface 22, 32 of each block, the wall having an inner surface, anouter surface, and a roof, as will be further discussed below.

A peripheral window 40 may be disposed between the adjoined blocks tolimit or tune coupling between adjacent through-holes 28 a, 38 of theadjoined blocks. The window may be configured to provide specificcoupling in terms of strength and frequency response depending on thechoice of window type and placement on the filter. The peripheral window40 defines an opening, and may be rectangular-shaped, square-shaped,cross-shaped, U-shaped, slit-shaped, oval-shaped, or circular shaped,among others.

Plural peripheral windows 40 may be provided along the length of themajor side surfaces of the blocks, such that each peripheral window isdisposed between adjacent through-holes of the adjacent blocks. Theperipheral windows 40 may be non-conductive cutouts in the metal-platedsidewalls of the ceramic filters. Moreover, depending on the choice ofwindow type and placement on the filter, unwanted couplings can beremoved, and skip-resonator filter designs may be permitted to improvefilter response. The windows 40 may be formed between individual platedblocks that are connected together, such as by sintering duringmanufacturing. Further, during manufacturing, only one block may beformed with the precise window cut, while the adjoined block if formedhaving an oversized window cut in order to ensure accuracy. When windowsare placed in the blocks before they are adjoined, one of the windowsmay be oversized to be larger than the similar (partner) window in theadjoining block. That way, when the blocks are joined, the smallerwindow will set the final size and position of the adjoined windows.This reduces the precision required in the alignment of the blocksduring assembly, and also improves the ease and quality ofmanufacturing.

The duplex filter may further comprise an in-line window 50 locatedwithin a block 20 of the pair of blocks and disposed between adjacentthrough-holes 28 b, 28 c of the block to limit or tune coupling betweenthe adjacent through-holes. The width of the in-line window 50 may belarger than a diameter of the adjacent through-holes 28 b, 28 c.Further, a height of the in-line window 50 may be smaller than alongitudinal length of the adjacent through-holes 28 b, 28 c. Thein-line window 50 may be rectangular-shaped, square-shaped,cross-shaped, U-shaped, slit-shaped, oval-shaped, or circular shaped,among others. Plural in-line windows 50 may be provided within one orboth of the blocks of the duplexer, such that each in-line window isdisposed between adjacent through-holes within the respective block.

In general, the size and shape of the peripheral and in-line windows 40,50 affects the performance of the filter. Both the peripheral andin-line windows allow energy to pass therethrough from one resonator toanother resonator. Thus, the windows 40, 50 couple energy from oneresonator to another. This coupling can also affect/tune the resonantfrequency of one or more nearby resonators. Therefore, a window couplinghaving a predetermined size and shape may be used to obtain optimalperformance. For instance, a small window coupling may provide weakcoupling between resonators, and a large window may provide a strongcoupling between resonators.

Turning to FIG. 2, a schematic view of a ceramic duplex filter 10′ inaccordance with another aspect of the present application isillustrated. The duplex filter 10′ includes a first block 20′ ofdielectric material and a second block 30′ of dielectric material. Eachblock 20′, 30′ includes a respective top surface 22′, 32′ having aconductive patterned region, a bottom surface 24′, 34′, and sidesurfaces 26′, 36′. The respective side surfaces 26′, 36′ further includemajor side surfaces 26 a′, 36 a′ and minor side surfaces 26 b′, 36 b′.The first and second blocks 20′, 30′ are adjoined at their respectivemajor side surfaces 26 a′, 36 a′. Each block 20′, 30′ also includesplural spaced apart through-holes 28′, 38′ extending through each blockfrom the top surface 22′, 32′ to the bottom surface 24′, 34′. Thethrough-holes are partially surrounded by the patterned region and actas resonators. Further, a wall extends from the top surface 22′, 32′ ofeach block, the wall having an inner surface, an outer surface, and aroof, as will be further discussed below.

At least one peripheral window 40′ may be disposed between the adjoinedblocks to limit or tune coupling between adjacent through-holes 28 a,′38′ of the adjoined blocks. Each peripheral window 40′ defines anopening, and may be rectangular-shaped, square-shaped, cross-shaped,U-shaped, slit-shaped, oval-shaped, or circular shaped, among others.The peripheral windows 40′ may be provided along the length of the majorside surfaces of the blocks, such that each peripheral window isdisposed between adjacent through-holes of the adjacent blocks.

At least one crenellation 60 may be provided on the major side surfaceof a block of the pair of blocks to limit or tune coupling betweenadjacent through-holes within the block and to reduce coupling betweennon-adjacent through-holes within the block. Corresponding crenellationsmay further be provided on the major side surface of the other block ofthe pair of blocks, such that a pair of crenellations may be aligned toform a hollow space therebetween. Each crenellation 60 defines a recesslocated on a major side surface of the block. As further shown in FIG.2, the ceramic duplex filter includes plural peripheral windows andplural crenellations that are alternatingly arranged along alongitudinal length of the pair of blocks. Further, the peripheralwindows 40′ and crenellations 60 are equidistantly spaced apart. Thecrenellation recess may be rectangular-shaped, square-shaped,cross-shaped, U-shaped, slit-shaped, oval-shaped, or circular shaped,among others.

FIG. 3 illustrates a duplex filter 200 that includes two radio frequency(RF) filters 100 in accordance with an aspect of the disclosure. Theduplex filter 200 may comprise at least one of the peripheral windows40, 40′ and/or at least one in-line window 50 previously describedabove. According another aspect, the duplex filter 200 may also, oralternatively, comprise at least one of the crenellations 60 previouslydescribed above. As shown in FIG. 3, the two simplex filters areadjoined along major side surfaces 112 creating a duplex filter. Inparticular, in each filter 100, a slot 210 is formed in the wall 114opposing the wall 114 having a post 235 formed therein. Because the slot210 is formed between two filters 100, the thickness of the slot 210 istwice the thickness of a slot 130 each filter.

In an embodiment, each of the filters 100 in the duplex filter 200includes a slot 220 (220 a is shown, and 220 b is not shown) on a minorside surface 111. The post 235 is formed between the two slots 220 a,220 b. In one embodiment, a portion of an inner wall of post 235 islocated adjacent slot 210. A top surface of the post extends betweenminor side surfaces 111 of two filters. A thickness of the post may varybetween the post's inner and outer walls.

Each filter 100 may be formed in any shape. In an exemplary embodimentshown in FIG. 3, each filter 100 has an elongate, parallelepiped orbox-shaped rigid block or core 110 comprised of a ceramic dielectricmaterial having a desired dielectric constant. Each filter 100 includesfour side surfaces. Two of the four side surfaces are minor sidesurfaces 111. The other two of the four side surfaces are major sidesurfaces 112. Each filter 100 also includes a bottom surface 115 and atop-recessed surface 120. The top surface 120 is generally parallel andopposed to the bottom surface.

Each filter 100 also includes four generally planar walls that extendupwardly from the top surface 120. In one embodiment, the planar wallsextend upwardly and/or outwardly along a perimeter of the top surface.In another embodiment, the planar walls are unitary portions of themajor 112 and minor 111 side surfaces. Planar walls of the minor sidesurfaces are 113, and planar walls of the major side surfaces are 114.Walls 113, 114, and top surface 120 define a cavity 125. Top surfaces113 a of wall 113 and top surfaces 114 a of wall 113 form a peripheralrim 115 of a predetermined thickness. The thickness of the roof isdependent upon the width and length of the cavity 125.

Inner walls 113 b of wall 113 of the minor surface 111, inner walls 114b of wall 114 of the major surface 112, and the top surface 120 can beplated or deposited with a first coating containing less frit content.The first coating will be described in more detail below.

In an embodiment, outer walls 113 c and 114 c of walls 113 and 114 arecoextensive and coplanar with major 111 and minor 112 surfaces,respectively. In one embodiment, the roof 113 a, 114 a are planar. Inanother embodiment, the roof slopes downward from the inner to outersurfaces of the walls 113, 114. In yet another embodiment, the roofslopes upward from the inner to outer surfaces of the walls 113, 114.The slope are be envisaged to be any angle.

As shown in FIG. 3, planar wall 114 includes plural, spaced-apart slots130. For example, the slots extend through the planar wall 114 from theinner 114 b to the outer 114 c surface. The slots 130 may have similaror different lengths extending between two minor side surfaces 111. Inan embodiment, a post 135 may be formed in the planar wall 114 betweentwo spaced-apart slots 130. The plural posts 135 may have similar ordifferent lengths.

The top surface 120 may include plural through-holes 150. Thethrough-holes 150 extend from the top surface 120 to the bottom surface115 (not shown) of the body 100. The through-holes 150 act asresonators. The though-holes are metallized. In an embodiment, thethrough-holes 150 are aligned in a spaced-apart, co-linear relationshipand are also equal distances from the side surfaces. Each ofthrough-holes 150 is defined by an inner cylindrical metallized sidewallsurface. The duplex filter 200 may include at least one peripheralwindow 40 disposed between resonators of adjacent blocks 100 and/or atleast one in-line window 50 disposed between adjacent resonators withineach block 100.

Top surface 120 additionally defines a surface-layer recessed pattern ofelectrically conductive metallized 121 a and insulative, un-metallized122 areas or patterns. The metallized areas 121 a are preferably asurface layer of conductive silver-containing material. Recessed pattern121 a defines a wide area or pattern of metallization that covers thesurface. In an embodiment, the recessed pattern 121 a, through-holes150, and inner walls 113 b, 114 b are deposited with a first coatingincluding a metal and frit. More specifically, the metal is a preciousmetal, such as silver (Ag).

The bottom surface 115, side surfaces 111, 112, outer planar walls 113c, 114 c, and top rim 113 a, 114 a are deposited with a second coatingincluding a metal and frit. The metal may be precious. In particular,the metal is silver (Ag). The frit content in the second coating may begreater than the first coating. In an embodiment, the frit content is atleast 20% greater in the second coating. In an exemplary embodiment, thefrit content is at least 25% greater in the second coating. In a furtherexemplary embodiment, the frit content is at least 30% greater in thesecond coating. In a yet a further exemplary embodiment, the fritcontent is at least 35% greater in the second coating. In even a furtherexemplary embodiment, the frit content is at least 40% greater in thesecond coating. The first coating also extends contiguously within thethrough-holes 150 from the top surface 120 to the bottom surface 115.

In an embodiment, a portion of metallized area 121 a is present in theform of resonator pads 121 a, 121 b, 121 c, 121 d, 121 d, 121 e and 121f (121 a is representative as illustrated by the reference indicator inthe drawing). Each of these resonator pads partially surrounds athrough-hole 150 a-f (150 a is representative as illustrated by thereference indicator in the drawing) opening located on the top, recessedsurface 120. In an exemplary embodiment, each resonator pad entirelysurrounds one of through-holes, respectively. The resonator pads arecontiguous with the metallization area 121 a that extends through theinner surfaces of the through-holes. Resonator pads 121 a-f (121 isrepresentative as illustrated by the reference indicator in the drawing)are shaped to have predetermined capacitive couplings to adjacentresonators and other areas of surface-layer metallization.

An un-metallized area or pattern 122 extends over portions of topsurface 120. Un-metallized area 122 surrounds all of the metallizedresonator pads 121 a-f. In addition, portions of inner planar walls 113b, 114 b and roofs 113 a, 114 a are un-metalized. Un-metallized area 122extends on the top surface 120 in slot 122 a (122 a is representative asillustrated by the reference indicator in the drawings). Theun-metallized area 122 also extends onto side wall slot portions 122 a′,122 a″, 122 b′, 122 b″, 122 c′, 122 c″, 122 d′ and 122 d″ (122 a′ and122 a″ are representative). Side wall slot portions 122 a′ and 122 a″define opposed sidewalls of the post 135.

In another embodiment, un-metallized area 122 also can also extend ontoa portion 123 of side surface 112 located below the post 135. Portion123 can also extend below the slots 130. These un-metallized areasco-extensive or joined or coupled with each other in an electricallynon-conducting relationship.

Surface-layer pattern 40 additionally defines a pair of isolatedconductive metallized areas 124 a, 124 b for input and outputconnections to filter 100. An input connection area or electrode 124 aand an output connection area or electrode 124 b are defined on topsurface 120 and extend onto a portion of the planar wall 114 and sidesurface 112. The electrodes can serve as surface mounting conductiveconnection points or pads or contacts. Electrodes 124 a, 124 b arelocated adjacent and parallel to side surfaces 111. Further, each of theelectrodes is located between two resonator pads 121 a-f. Electrodes 124a, 124 b are surrounded on all sides by un-metallized areas 122.

In another embodiment, the recessed surface pattern 120 includesmetallized 121 areas and un-metallized 122 areas. As a result,metallized areas are spaced apart from one another and capacitivelycoupled. The amount of capacitive coupling is roughly related to thesize of the metallization areas and the separation distance betweenadjacent metallized portions as well as the overall core configurationand the dielectric constant of the core dielectric material. Similarly,surface pattern 120 also creates inductive coupling between themetallized areas.

According to other aspects of the disclosure, a system 300 may comprisethe duplex filter 200 and a printed circuit board (PCB) 310 having a topsurface and including input and output pads, as will be furtherdescribed below. In other implementations, the system 300 may comprisethe duplex filter 10, 10′ previously described. As shown in FIG. 4,duplex filter 200 is illustrated as being mounted to a generally planarrectangular shaped circuit board 310. In one embodiment, circuit board310 is a printed circuit board having a top or top surface 310 a, bottomor bottom surface 310 b and sides or side surfaces 310 c. Circuit board310 has a height of a predetermined thickness. Circuit board 310 alsoincludes plated through-holes 315 that form an electrical connectionbetween the top and the bottom of the circuit board 310. Several circuitlines 320 and input/output connection pads 321 can be located on top thetop surface and connected with terminals 322. Circuit lines 320,connection pads 321, and terminals 322 can be formed, for example, frommetal such as copper. Terminals 322 connect the duplex filter 200 withan external electrical circuit (not shown).

A post of the duplex filter 200 can be attached to the PCB 310 at theconnection pad(s) 321 by solder 330. In an embodiment, one or both ofthe input 124 a and output 124 b electrodes can be attached to thesolder 330.

Circuit board 310 has a generally rectangular-shaped ground ring or line340. It can be disposed on the top surface. The line 340 can be formedaround the rim of the filter. The ground ring can be formed from copper.Next, the duplex filter 200 can be placed on top such that inputelectrode portion 124 a and output electrode portion 124 b are alignedwith connection pads 321. Circuit board 310 and duplex filter 200 may bearranged in a reflow oven to melt and reflow the solders.

As illustrated in FIG. 4, duplex filter 200 is mounted to the board 310in a top side down relationship. As a result, the top surface 120 islocated opposite, parallel to, and spaced from the top 310 of board andthe rim of 113 a, 114 a of the filter are soldered to the top of thePCB. In this relationship, cavity 125 is partially sealed to define anenclosure defined by the top, recessed surface 120, the board surface310 a, and the walls 111, 112 of the filter. It is further noted that,in this relationship, the through-holes in the filter are oriented in arelationship generally normal to the board 310.

The use of duplex filter 200 with recessed top surface pattern 120facing and opposite the board 310 provides improved grounding and offband signal absorption; and confines the electromagnetic fields withincavity 125. The arrangement also prevents external electromagneticfields outside of cavity 125 from causing noise and interference suchthat the attenuation and zero points of the filter are improved. Thearrangement of the cavity also prevents the electromagnetic fields frominterfering and coupling with other components mounted near filter 200.The technology allows the same footprint to be used across multiplefrequency bands. In addition, during solder reflow, filter 200 tends toself-align with the ground ring 340 on the circuit board. The Filterexhibits improved self-alignment since the surface tension of the liquidsolder during reflow is distributed equally around roof between theground ring and rim providing self-centering of the filter's core 110.

The use of a duplex filter 200 defining a cavity and a recessed topsurface pattern 40 facing and opposite the board eliminates the need fora separate external metal shield or other shielding as currently used toreduce spurious electromagnetic interference incurred.

Recessed pattern creates a resonant circuit that includes a capacitanceand an inductance in series connected to ground. The shape of patterndetermines the overall capacitance and inductance values. Thecapacitance and inductance values are designed to form a resonantcircuit that suppresses the frequency response at frequencies outsidethe passband including various harmonic frequencies at integer intervalsof the passband.

According to an aspect of the disclosure, a signal may be communicate toand from a node by providing a duplex filter, receiving the signal intothe duplex filter from the node; transmitting the signal betweenadjacent through-holes within adjoined blocks of the duplex filter bypassing the signal through a peripheral window located on a major sidesurface of the duplex filter; and sending the signal from the duplexfilter out to the node. The signal may further be transmitted betweenadjacent through-holes within a block of the duplex filter by passingthe signal through an in-line window located within the block.Additionally, or alternatively, the signal may be transmitted betweenadjacent through-holes within a block of the duplex filter by passingthe signal by a crenellation located on a major side surface of theblock.

While the apparatus, system, and method have been described in terms ofwhat are presently considered to be specific embodiments, the disclosureneed not be limited to the disclosed embodiments. It is intended tocover various modifications and similar arrangements included within thespirit and scope of the claims, the scope of which should be accordedthe broadest interpretation so as to encompass all such modificationsand similar structures. The present disclosure includes any and allembodiments of the following claims.

What is claimed is:
 1. A duplex filter comprising: a pair of adjoinedblocks of dielectric material, each block having a top surface includinga conductive patterned region, a bottom surface, and side surfaces;plural spaced apart through-holes extending through each block from thetop surface to the bottom surface, the through-holes being partiallysurrounded by the patterned region; and a wall extending from the topsurface of each block, the wall having an inner surface, an outersurface, and a roof; and a peripheral window disposed between theadjoined blocks to permit a coupling between adjacent through-holes ofthe adjoined blocks.
 2. The duplex filter according to claim 1, furthercomprising an in-line window located within a block of the pair ofblocks and disposed between adjacent through-holes of the block to limitor tune coupling between the adjacent through-holes.
 3. The duplexfilter according to claim 2, wherein a width of the in-line window islarger than a diameter of the adjacent through-holes.
 4. The duplexfilter according to claim 3, wherein a height of the in-line window issmaller than a longitudinal length of the adjacent through-holes.
 5. Theduplex filter according to claim 2, wherein the in-line window isrectangular-shaped, square-shaped, cross-shaped, U-shaped, slit-shaped,oval-shaped, or circular shaped.
 6. The duplex filter according to claim1, further comprising a crenellation on the side surface of a block ofthe pair of blocks to limit or tune coupling between adjacentthrough-holes within the block and to reduce coupling betweennon-adjacent through-holes within the block.
 7. The duplex filteraccording to claim 6, further comprising a corresponding crenellation onthe side surface of the other block of the pair of blocks, such that thepair of crenellations are aligned and form a hollow space therebetween.8. The duplex filter according to claim 6, wherein the crenellationdefines a recess located on a major side surface of the block.
 9. Theduplex filter according to claim 8, further comprising plural peripheralwindows and plural crenellations alternatingly arranged along a lengthof the pair of blocks.
 10. The duplex filter according to claim 9,wherein the peripheral windows and crenellations are equidistantlyspaced apart.
 11. The duplex filter according to claim 8, wherein therecess is rectangular-shaped, square-shaped, cross-shaped, U-shaped,slit-shaped, oval-shaped, or circular shaped.
 12. The duplex filteraccording to claim 1, wherein the peripheral window isrectangular-shaped, square-shaped, cross-shaped, U-shaped, slit-shaped,oval-shaped, or circular shaped.
 13. The duplex filter according toclaim 1, wherein the peripheral window defines an opening.
 14. A systemcomprising: a printed circuit board having a top surface and includinginput and output connections; and a duplex filter including: a pair ofadjoined blocks of dielectric material, each block having a top surfaceincluding a conductive patterned region, a bottom surface, and sidesurfaces; plural spaced apart through-holes extending through each blockfrom the top surface to the bottom surface, the through-holes beingpartially surrounded by the patterned region; and a wall extending fromthe top surface of each block, the wall having an inner surface, anouter surface, and a roof; and a peripheral window disposed between theadjoined blocks to limit or tune coupling between adjacent through-holesof the adjoined blocks.
 15. The system according to claim 14, whereinthe duplex filter further comprises an in-line window located within ablock of the pair of blocks and disposed between adjacent through-holesof the block to limit or tune coupling between the adjacentthrough-holes.
 16. The system according to claim 14, wherein the duplexfilter further comprises a crenellation on the side surface of a blockof the pair of blocks to limit or tune coupling between adjacentthrough-holes within the block and to reduce coupling betweennon-adjacent through-holes within the block.
 17. The system according toclaim 16, wherein the duplex filter further comprises plural peripheralwindows and plural crenellations alternatingly arranged along a lengthof a major side surface of the pair of blocks.
 18. A method ofcommunicating with a node, the method comprising: providing a duplexfilter according to claim 1; receiving the signal into the duplex filterfrom the node; transmitting the signal between adjacent through-holeswithin adjoined blocks of the duplex filter by passing the signalthrough a peripheral window located on a major side surface of theduplex filter; and sending the signal from the duplex filter out to thenode.
 19. The method of communicating with a node according to claim 18,further comprising transmitting the signal between adjacentthrough-holes within a block of the duplex filter by passing the signalthrough an in-line window located within the block.
 20. The method ofcommunicating with a node according to claim 18, further comprisingtransmitting the signal between adjacent through-holes within a block ofthe duplex filter by passing the signal by a crenellation located on amajor side surface of the block.